Conventionally, a direct conversion type radiation detector which converts radiation directly into carriers (charge information) in a semiconductor layer applies a predetermined bias voltage to a common electrode layer formed on a front surface of the semiconductor layer which is sensitive to radiation, and collects the carriers thereby generated in the semiconductor layer in picture electrodes formed on a back surface of the semiconductor layer. Further, the carriers collected are read as radiation detection signals, using an active matrix substrate, thereby to detect the radiation.
An amorphous semiconductor layer such as a-Se (amorphous selenium), for example, is used as the radiation sensitive semiconductor layer.
Since the direct conversion type radiation detector applies a high voltage to the common electrode layer, a discharge occurs along the surface of the amorphous semiconductor layer. In order to solve the problem of this creeping discharge, in Patent Document 1 and in FIG. 5, entire surfaces of an amorphous semiconductor layer 51, a common electrode layer 52 and a carrier selective high resistance film 53 are covered with an insulating layer 55 of high withstand voltage (epoxy resin). An active matrix substrate 54 covers a lower surface of the amorphous semiconductor layer 51.
Further, Patent Document 1 also indicates a problem that solvent components of the epoxy resin react with a-Se forming the amorphous semiconductor layer 51, to discolor the surface of the amorphous semiconductor layer 51, and lower the withstand voltage. So, the entire surface of the amorphous semiconductor layer 51 is covered with the solvent-resistant and carrier selective high resistance film 53 such as Sb2S3 film, to reduce the reaction between the solvent components of the epoxy resin and a-Se and to prevent alteration of the surface of the amorphous semiconductor layer 51 and lowering of the withstand voltage.
[Patent Document 1]
Unexamined Patent Publication No. 2002-311144